Hydrogenated isotopically enriched boront trifluoride dopant source gas composition

ABSTRACT

A hydrogenated isotopically enriched boron trifluoride (BF3) dopant source gas composition. The composition contains (i) boron trifluoride isotopically enriched above natural abundance in boron of atomic mass 11 (UB), and (ii) hydrogen in an amount of from 2 to 6.99 vol. %, based on total volume of boron trifluoride and hydrogen in the composition. Also described are methods of use of such dopant source gas composition, and associated apparatus therefor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to International Application No.PCT/EP2017/024312, filed Mar. 27, 2017 and titled “HYDROGENATEDISOTOPICALLY ENRICHED BORONT TRIFLUORIDE DOPANT SOURCE GAS COMPOSITION,”which in turn claims priority from a Provisional Application having Ser.No. 62/314,241, filed Mar. 28, 2016 and titled “HYDROGENATEDISOTOPICALLY ENRICHED BORONT TRIFLUORIDE DOPANT SOURCE GAS COMPOSITION,”both of which are incorporated herein by reference in their entireties.

TECHNICAL FIELD

The disclosure relates to a hydrogenated isotopically enriched borontrifluoride (BF₃) dopant source gas composition for use in ionimplantation, and to associated methods and apparatus.

BACKGROUND

Ion implantation is used in integrated circuit fabrication to accuratelyintroduce controlled amounts of dopant impurities into semiconductorwafers during the manufacture of microelectronic/semiconductormanufacturing. In such implantation systems, an ion source ionizes adesired dopant element gas, and the ions are extracted from the sourcein the form of an ion beam of desired energy. Extraction is achieved byapplying a high voltage across suitably-shaped extraction electrodes,which incorporate apertures for passage of the extracted beam. The ionbeam is then directed at the surface of a workpiece, such as asemiconductor wafer, to implant the dopant elements into the workpiece.The ions of the beam penetrate the surface of the workpiece to form aregion of desired conductivity.

Several types of ion sources are used in ion implantation systems,including the Freeman and Bernas types that employ thermoelectrodes andare powered by an electric arc, microwave types using a magnetron,indirectly heated cathode (IHC) sources, and RF plasma sources, all ofwhich typically operate in a vacuum. In any system, the ion sourcegenerates ions by introducing electrons into a vacuum arc chamber(hereinafter “chamber”) filled with the dopant gas (commonly referred toas the “feedstock gas”). Collisions of the electrons with atoms andmolecules in the dopant gas result in the creation of ionized plasmaconsisting of positive and negative dopant ions. An extraction electrodewith a negative or positive bias will respectively allow the positive ornegative ions to pass through an aperture as a collimated ion beam,which is accelerated towards the target material.

In many ion implantation operations, boron is implanted in theproduction of integrated circuit devices. The boron is generallyimplanted from a feedstock gas such as boron trifluoride.

Tungsten is commonly used as a material of construction for filamentelements and other cathode structures in ion implantation systems. Apersistent problem in use of such material in the ion source chamber ofthe ion implantation system is that of tungsten loss, which can resultin filament thinning or so-called “punch through” of the cathodestructure, requiring re-metallization or replacement of the cathodestructure. In extreme cases, sputtering of tungsten from the cathode canresult in extremely short operating life of the ion source before suchre-metallization or replacement is needed. The loss of tungsten from thecathode is associated with unwanted deposition of tungsten on the ionsource chamber surfaces and unwanted tungsten beam contributions to theion beam generated in the system. The loss of tungsten thus can be acontributor to ion beam instability, and may eventually cause prematurefailure of the ion source.).

SUMMARY

The present disclosure relates to a hydrogenated isotopically enrichedboron trifluoride (BF₃) dopant source gas composition for use in ionimplantation, and to associated methods and apparatus.

In one aspect, the disclosure relates to a hydrogenated isotopicallyenriched boron trifluoride (BF₃) dopant source gas composition including(i) boron trifluoride isotopically enriched above natural abundance inboron of atomic mass 11 (¹¹B), and (ii) hydrogen in an amount of from 2to 6.99 vol. %, based on total volume of boron trifluoride and hydrogenin said composition.

In another aspect, the disclosure relates to a hydrogenated isotopicallyenriched boron trifluoride (BF₃) dopant source gas composition including(i) boron trifluoride isotopically enriched above 99% in boron of atomicmass 11 (¹¹B), and (ii) hydrogen in an amount of 5 vol. %, based ontotal volume of boron trifluoride and hydrogen in said composition.

In a further aspect, the disclosure relates to a hydrogenatedisotopically enriched boron trifluoride (BF₃) dopant source gascomposition, said composition consisting essentially of (i) borontrifluoride isotopically enriched above natural abundance in boron ofatomic mass 11 (¹¹B), and (ii) hydrogen in an amount of from 2 to 6.99vol. %, based on total volume of boron trifluoride and hydrogen in suchcomposition. More particularly, hydrogen may be present in any suitableamount, ranging from 2 to 6.5 vol. %, based on total volume of borontrifluoride and hydrogen in such composition, ranging from 2.5 to 6.25vol. %, based on total volume of boron trifluoride and hydrogen in suchcomposition, ranging from 3 to 6 vol. %, based on total volume of borontrifluoride and hydrogen in such composition, from about 4 to 6 vol. %or in an amount of 5 vol. %, based on total volume of boron trifluorideand hydrogen in said composition, it being appreciated that the specificamount, or utilized range of such amount, may be selected for specificapplications to achieve a desired level of operational performance orenhancement.

A further aspect of the disclosure relates to a boron dopant gascomposition supply package including a gas storage and dispensing vesselcontaining a hydrogenated isotopically enriched boron trifluoride (BF₃)dopant source gas composition according to the various embodiments asdisclosed herein.

A still further aspect of the disclosure relates to method of forming aboron-implanted substrate, comprising ionizing a hydrogenatedisotopically enriched boron trifluoride (BF₃) dopant source gascomposition according to the various embodiments as disclosed herein, togenerate boron-containing ionic implant species, and implanting suchboron-containing implant species in the substrate.

A further aspect of the disclosure relates to a method of boron ionimplantation, including introducing to an ion source chamber of an ionimplantation system a hydrogenated isotopically enriched borontrifluoride (BF₃) dopant source gas composition according to the variousembodiments disclosed herein, and ionizing such hydrogenatedisotopically enriched boron trifluoride (BF₃) dopant source gascomposition in the ion source chamber to generate boron-containingimplant species for the boron ion implantation.

The disclosure relates in a further aspect to a method of enhancingoperation of an ion implantation system, including flowing a borondopant gas composition to an ion implantation system from a boron dopantgas supply package including a gas storage and dispensing vessel holdinga hydrogenated isotopically enriched boron trifluoride (BF₃) dopantsource gas composition according to the various embodiments of thedisclosure as described herein.

Another aspect of the disclosure relates to a method of reducingtungsten cathode erosion in a boron ion implantation system having atungsten cathode, the method including generating boron implant speciesfor boron ion implantation within the system by ionization of ahydrogenated isotopically enriched boron trifluoride (BF₃) dopant sourcegas composition according to the various embodiments of the disclosureas described herein.

Yet another aspect of the disclosure relates to a method of enhancingoperational performance of a boron ion implantation system, includingsupplying for use in the boron ion implantation system a boron dopantsource gas composition including a hydrogenated isotopically enrichedboron trifluoride (BF₃) dopant source gas composition according to thevarious embodiments of the disclosure as described herein.

In a further aspect, the disclosure relates to a method of enhancingoperational performance of a boron ion implantation system, includinggenerating boron implant species in the boron ion implantation systemfrom a boron dopant source gas composition including a hydrogenatedisotopically enriched boron trifluoride (BF₃) dopant source gascomposition according to the various embodiments of the disclosure asdescribed herein.

The disclosure in a further aspect relates to a method of enhancing beamstability and ion source life of a boron doping ion implantation systemcomprising a cathode, the method including introducing a boron dopantsource gas composition to an ion source chamber of the boron doping ionimplantation system, operating the boron doping ion implantation systemto ionize the boron dopant source gas composition in the ion sourcechamber and generate a beam of boron dopant species that is directed toa substrate in the ion implantation system for boron doping of thesubstrate therein with the boron dopant species, wherein the dopantsource gas composition includes (i) boron trifluoride isotopicallyenriched above natural abundance in boron of atomic mass 11 (¹¹B), and(ii) hydrogen in an amount of from 2 to 6.99 vol. %, based on totalvolume of boron trifluoride and hydrogen in such composition, wherein areduction in beam current is less than 8%. More particularly, hydrogenmay be present in any suitable amount, ranging from 2 to 6.5 vol. %,based on total volume of boron trifluoride and hydrogen in suchcomposition, ranging from 2.5 to 6.25 vol. %, based on total volume ofboron trifluoride and hydrogen in such composition, ranging from 3 to 6vol. %, based on total volume of boron trifluoride and hydrogen in suchcomposition, from about 4 to 6 vol. % or in an amount of 5 vol. %, basedon total volume of boron trifluoride and hydrogen in said composition,it being appreciated that the specific amount, or utilized range of suchamount, may be selected for specific applications to achieve a desiredlevel of operational performance or enhancement.

In yet another aspect, the disclosure relates to a method of operatingan ion implantation system, including co-flowing (a) ¹¹B-isotopicallyenriched boron trifluoride from a first gas supply package, and (b)hydrogen gas from a second gas supply package, to an ion source chamberof the ion implantation system, at relative rates of the borontrifluoride and hydrogen gases to constitute a dopant source gascomposition in the ion source chamber comprising (i) boron trifluorideisotopically enriched above natural abundance in boron of atomic mass 11(¹¹B), and (ii) hydrogen in an amount of from 2 to 6.99 vol. %, based ontotal volume of boron trifluoride and hydrogen in such composition. Moreparticularly, hydrogen may be present in any suitable amount, rangingfrom 2 to 6.5 vol. %, based on total volume of boron trifluoride andhydrogen in such composition, ranging from 2.5 to 6.25 vol. %, based ontotal volume of boron trifluoride and hydrogen in such composition,ranging from 3 to 6 vol. %, based on total volume of boron trifluorideand hydrogen in such composition, from about 4 to 6 vol. % or in anamount of 5 vol. %, based on total volume of boron trifluoride andhydrogen in said composition, it being appreciated that the specificamount, or utilized range of such amount, may be selected for specificapplications to achieve a desired level of operational performance orenhancement.

The preceding summary is provided to facilitate an understanding of someof the innovative features unique to the present disclosure and is notintended to be a full description. A full appreciation of the disclosurecan be gained by taking the entire specification, claims, drawings, andabstract as a whole.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing description of various illustrative embodiments in connectionwith the accompanying drawings.

FIG. 1 is a schematic cross-sectional view of a fluid supply packageincluding a pressure-regulated fluid storage and dispensing vessel inwhich the hydrogenated enriched boron trifluoride dopant source gascomposition according to the various embodiments of present disclosuremay be provided for storage and dispensing of the composition.

FIG. 2 is a schematic representation of an ion implantation systemillustrating modes of operation according to the present disclosure inwhich in which a hydrogenated enriched boron trifluoride dopant sourcegas composition of the present disclosure is supplied to an ionimplanter for implantation of boron in a substrate.

FIG. 3 is a graph of B+ beam current, as a function of hydrogen/borontrifluoride co-flow ratio (volume H₂/volume BF₃ from 0 to 0.6) flowed toan ion chamber of an ion implantation apparatus, with an isotopicallyenriched BF₃ flow rate of 2.75 standard cubic centimeters per minute(sccm), showing the beam performance of hydrogenated isotopicallyenriched boron trifluoride dopant source gas compositions according tothe various embodiments of the present disclosure.

FIG. 4 is a beam spectrum comparison graph, of beam current, inmilliamps, as a function of atomic mass unit (AMU) value, showing beamcurrent values for B+, F+, HF+, BF+, BF2+, and W++ ions, with an insetspectrum segment showing the beam current values for W+ and WF_(x)+(x=1, 2, 3, 4, 5, and 6) ions in the range of 170-300 AMU, as shown for(i) flow of only substantially pure (>99.95 vol. %) ¹¹BF₃, (ii) co-flowof hydrogen with the substantially pure (>99.95 vol. %) ¹¹BF₃, at a lowH₂/¹¹BF₃ volumetric ratio, and (iii) co-flow of hydrogen with thesubstantially pure (>99.95 vol. %) ¹¹BF₃, at a high H₂/¹¹BF₃ volumetricratio.

FIG. 5 is a graph of F+, HF+, W+, and WF+ beam currents, in milliamps,as a function of H₂/¹¹BF₃ volumetric ratio from 0 to 0.6, wherein datafor the respective ion species are represented by diamond symbols (♦)for F+, circular dot symbols (●) for HF+, square symbols (▪) for W+, andtriangular symbols (▴) for WF+. The boron trifluoride employed togenerate such data was substantially pure (>99.95 vol. %) ¹¹BF₃.

FIG. 6 is a graph of the corresponding normalized F+, HF+, W+, and WF+beam currents, in milliamps, as a function of H₂/¹¹BF₃ volumetric ratiofrom 0 to 0.6, where x is a coefficient for the H₂/BF₃ ratio, whereinF+, HF+, W+, and WF+ beam currents have been normalized to B+ beamcurrents, with data for the respective ion species are represented bydiamond symbols (▴) for F+, circular dot symbols (●) for HF+, squaresymbols (▪) for W+, and triangular symbols (▴) for WF+.

FIG. 7 is a beam spectrum comparison graph, of beam current, inmilliamps, as a function of atomic mass unit (AMU) value, showing beamcurrent values for B+, F+, BF+, and BF2+ ions, with an inset spectrumsegment showing the beam current values for W+ and WF_(x)+ (x=1, 2, 3,4, 5, and 6) ions in the range of 170-300 AMU, in which the ionimplantation system was tuned for B+ ion implant species in a first run,and for BF₂+ ion implant species in a second run, utilizingnon-hydrogenated substantially pure (>99.95 vol. %) ¹¹BF₃ in both cases.

FIG. 8 is a beam spectrum comparison graph, of beam current, inmilliamps, as a function of atomic mass unit (AMU) value, showing beamcurrent values for B+, F+, BF+, and BF2+ ions, with an inset spectrumsegment showing the beam current values for W+ and WF_(x)+ (x=1, 2, 3,4, 5, and 6) ions in the range of 170-300 AMU, in which the ionimplantation system was tuned for B+ ion implant species, utilizingnon-hydrogenated substantially pure (>99.95 vol. %) ¹¹BF₃ (greenspectrum) in a first run, and hydrogenated substantially pure (>99.95vol. %) ¹¹BF₃ (red spectrum; H₂/¹¹BF₃ volumetric at optimized ratio of0.05) in a second run.

FIG. 9 is a beam spectrum comparison graph, of beam current, inmilliamps, as a function of atomic mass unit (AMU) value, showing beamcurrent values for B+, F+, BF+, and BF2+ ions, with an inset spectrumsegment showing the beam current values for W+ and WF_(x)+ (x=1, 2, 3,4, 5, and 6) ions in the range of 170-300 AMU, in which the ionimplantation system was tuned for BF₂+ ion implant species, utilizingnon-hydrogenated substantially pure (>99.95 vol. %) ¹¹BF₃ (greenspectrum) in a first run, and hydrogenated substantially pure (>99.95vol. %) ¹¹BF₃ (red spectrum; H₂/¹¹BF₃ volumetric at optimized ratio of0.05) in a second run.

FIG. 10 is a graph showing the cathode weight change per hour plottedagainst the volume percentage of hydrogen gas where the implanting ionis B+.

FIG. 11 is a graph showing the anti-cathode weight change per hourplotted against the volume percentage of hydrogen gas wherein theimplanting ion is B+.

FIG. 12 is a graph showing the cathode weight change per hour plottedagainst the volume percentage of hydrogen gas where the implanting ionis BF₂+.

FIG. 13 is a graph showing the anti-cathode weight change per hourplotted against the volume percentage of hydrogen gas where theimplanting ion is BF₂+.

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit aspects of thedisclosure to the particular illustrative embodiments described. On thecontrary, the intention is to cover all modifications, equivalents, andalternatives falling within the spirit and scope of the disclosure.

DESCRIPTION

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The detailed description and the drawings, which are notnecessarily to scale, depict illustrative embodiments and are notintended to limit the scope of the disclosure. The illustrativeembodiments depicted are intended only as exemplary. Selected featuresof any illustrative embodiment may be incorporated into an additionalembodiment unless clearly stated to the contrary.

As used herein, and in the appended claims, the singular forms “a”,“and”, and “the” include plural referents unless the context clearlydictates otherwise.

As used herein, the term “pressure-regulated” in reference to fluidstorage and dispensing vessels means that such vessels have at least onepressure regulator device, set pressure valve, or vacuum/pressureactivated check valve disposed in an interior volume of the vesseland/or in a valve head of the vessel, with each such pressure regulatordevice being adapted so that it is responsive to fluid pressure in thefluid flow path immediately downstream of the pressure regulator device,and opens to enable fluid flow at a specific downstream reduced pressurecondition in relation to the higher fluid pressure upstream of thepressure regulator device, and subsequent to such opening operates tomaintain the pressure of fluid discharged from the pressure regulatordevice at a specific, or “set point,” pressure level.

The present disclosure relates to a hydrogenated isotopically enrichedboron trifluoride (BF3) dopant source gas composition having utility inion implantation for generating ionic boron species for implantation insubstrates, and to associated methods and apparatus, whereby highefficiency ion implantation can be carried out in the manufacture ofproducts such as semiconductor devices, flat panel displays, and solarpanels. The hydrogenated isotopically enriched boron trifluoridecompositions of the present disclosure enable high boron ion beamcurrents to be maintained, while substantially reducing the amount ofundesired beam components including tungsten and tungsten fluoride ionicspecies, to enable source life of the cathode to be extended, therebyenhancing the high-efficiency obtained by use of isotopically enrichedboron trifluoride, and reducing the maintenance required by the ionimplantation equipment, e.g., with respect to cathode re-metallizationand replacement.

The hydrogenated isotopically enriched boron trifluoride compositions ofthe present disclosure may in various embodiments comprise, consistessentially of, or consist of the boron trifluoride and hydrogencomponents that are variously disclosed herein. In any of thecompositions, methods, and apparatus disclosed herein, which aredescribed as comprising components, parts, or subassemblies, it will beappreciated that other embodiments of such compositions, methods, andapparatus may be employed, as consisting or consisting essentially ofsuch components, parts, or assemblies, as applicable.

In one embodiment, the present disclosure relates to a hydrogenatedisotopically enriched boron trifluoride (BF₃) dopant source gascomposition, including (i) boron trifluoride isotopically enriched abovenatural abundance in boron of atomic mass 11 (¹¹B), and (ii) hydrogen inan amount of from 2 to 6.99 vol. %, based on total volume of borontrifluoride and hydrogen in the composition.

In various embodiments of the hydrogenated isotopically enriched borontrifluoride (BF₃) dopant source gas composition of the presentdisclosure, the boron trifluoride isotopically enriched above naturalabundance in boron of atomic mass 11 (¹¹B) may be isotopically enrichedabove an enrichment level selected from the group consisting of 80.1%,85%, 88%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, 99.995%,and 99.999%.

In other embodiments of the hydrogenated isotopically enriched borontrifluoride (BF₃) dopant source gas composition of the presentdisclosure, the boron trifluoride isotopically enriched above naturalabundance in boron of atomic mass 11 (¹¹B) may be isotopically enrichedat an enrichment level in a range selected from the group consisting of81-85%, 85-90%, 90-95%, 95-99%, and 95-100%.

In various embodiments of the disclosure, the boron trifluorideisotopically enriched above natural abundance in boron of atomic mass 11(¹¹B) is 100% isotopically enriched.

In one aspect, the disclosure relates to a hydrogenated isotopicallyenriched boron trifluoride (BF₃) dopant source gas composition including(i) boron trifluoride isotopically enriched above 99% in boron of atomicmass 11 (¹¹B), and (ii) hydrogen in an amount of 5 vol. %, based ontotal volume of boron trifluoride and hydrogen in said composition.

In another aspect, the disclosure relates to a hydrogenated isotopicallyenriched boron trifluoride (BF₃) dopant source gas compositionconsisting essentially of (i) boron trifluoride isotopically enrichedabove natural abundance in boron of atomic mass 11 (¹¹B), and (ii)hydrogen in an amount of from 2 to 6.99 vol. %, based on total volume ofboron trifluoride and hydrogen in such composition.

In various embodiments of the above-described hydrogenated isotopicallyenriched boron trifluoride (BF₃) dopant source gas composition, hydrogenmay be present in any suitable amount, ranging from 2 to 6.5 vol. %,based on total volume of boron trifluoride and hydrogen in suchcomposition, ranging from 2.5 to 6.25 vol. %, based on total volume ofboron trifluoride and hydrogen in such composition, ranging from 3 to 6vol. %, based on total volume of boron trifluoride and hydrogen in suchcomposition, from about 4 to 6 vol. % or in an amount of 5 vol. %, basedon total volume of boron trifluoride and hydrogen in said composition,it being appreciated that the specific amount, or utilized range of suchamount, may be selected for specific applications to achieve a desiredlevel of operational performance or enhancement.

A further aspect of the disclosure relates to a boron dopant gascomposition supply package including a gas storage and dispensing vesselholding a hydrogenated isotopically enriched boron trifluoride (BF₃)dopant source gas composition according to the various embodiments ofthe disclosure as disclosed herein.

Such supply package may be constituted, wherein the gas storage anddispensing vessel comprises an internally pressure-regulated gas storageand dispensing vessel, e.g., wherein the internally pressure-regulatedgas storage and dispensing vessel has internally disposed therein aseries arrangement of gas pressure regulators through which gas flows indispensing operation of the package, as for example may be employed fordispensing of the hydrogenated isotopically enriched boron trifluoride(BF₃) dopant source gas composition at sub-atmospheric pressure.Alternatively, the internally pressure-regulated gas storage anddispensing vessel may be configured to deliver the dopant source gascomposition at suitable pressure level in a range of from atmospheric tolow superatmospheric pressure, e.g., from atmospheric pressure up to 200psig (1.38 Megapascal (MPa)), or in a low superatmospheric pressurerange, such as from 10 psig (0.069 MPa) to 200 psig (1.38 MPa), or inother embodiments, from 50 psig (0.0345 MPa) to 150 psig (1.034 MPa).

The disclosure further contemplates a method of forming aboron-implanted substrate, including ionizing a hydrogenatedisotopically enriched boron trifluoride (BF₃) dopant source gascomposition of the present disclosure, as variously described herein, togenerate boron-containing ionic implant species, and implanting suchboron-containing implant species in the substrate. The boron-containingionic implant species may be of any suitable type, and may for examplecomprise B+, B++, B+++, BF₂+, BF₂++, or any other advantageous boronimplant species.

A further aspect of the disclosure relates to a method of boron ionimplantation including introducing to an ion source chamber of an ionimplantation system a hydrogenated isotopically enriched borontrifluoride (BF₃) dopant source gas composition according to the presentdisclosure, as variously described herein, and ionizing suchhydrogenated isotopically enriched boron trifluoride (BF₃) dopant sourcegas composition in the ion source chamber to generate boron-containingimplant species for the boron ion implantation. The method may furtherincluding generating a beam of the boron-containing implant species, anddirecting the beam to a substrate for implantation of theboron-containing implant species therein. The method alternatively mayinclude exposing a substrate to the boron-containing implant species,for implantation thereof in the substrate, with such exposure includingany appropriate process or technique, such as plasma-assisted ionimplantation, beamline implantation with mass analyzer, beamlineimplantation without mass analyzer, plasma immersion, etc.

The above-discussed methods may be conducted in a process formanufacture of a product selected from the group consisting ofsemiconductor products, flat-panel display products, and solar panelproducts.

The disclosure relates in a further aspect to a method of enhancingoperation of an ion implantation system including providing for use inthe ion implantation system a boron dopant gas composition supplypackage comprising a gas storage and dispensing vessel holding ahydrogenated isotopically enriched boron trifluoride (BF₃) dopant sourcegas composition according to the various embodiments as disclosedherein.

Another aspect of the disclosure relates to a method of reducingtungsten cathode erosion in a boron ion implantation system having atungsten cathode, such method including generating boron implant speciesfor boron ion implantation in the system by ionization of a hydrogenatedisotopically enriched boron trifluoride (BF₃) dopant source gascomposition according to the various embodiments as disclosed herein.

Yet another aspect of the disclosure relates to a method of enhancingoperational performance of a boron ion implantation system includingsupplying for use in the boron ion implantation system a boron dopantsource gas composition comprising a hydrogenated isotopically enrichedboron trifluoride (BF₃) dopant source gas composition according to thevarious embodiments as disclosed herein.

In a further aspect, the disclosure relates to a method of enhancingoperational performance of a boron ion implantation system includinggenerating boron implant species in the boron ion implantation systemfrom a boron dopant source gas composition comprising a hydrogenatedisotopically enriched boron trifluoride (BF₃) dopant source gascomposition according to the various embodiments as disclosed herein.

Accordingly, the present disclosure contemplates hydrogen/enriched borontrifluoride dopant source gas compositions for ion implantation ofboron, in which the composition contains from 2 to 6.99 volume percentof hydrogen, as a compositional range in which beam current reduction ismaintained at a very low level, e.g., in a range of from 0% to 8%reduction of the boron ion beam current, while the production of F+, W+,and WF_(x)+ beam components is surprisingly effectively reduced. Thereduction in boron ion beam current can be determined by comparing theboron ion beam current when hydrogen is present in the dopant gas inselected amounts to the boron ion beam current in the absence ofhydrogen. Accordingly, the hydrogenated isotopically enriched borontrifluoride compositions of the present disclosure enable high boron ionbeam currents to be maintained, while substantially reducing the amountof undesired beam components including tungsten and tungsten fluorideionic species, to enable source life of the cathode to be dramaticallyextended, thereby enhancing the high-efficiency obtained by use ofisotopically enriched boron trifluoride, and dramatically reducing themaintenance required by the ion implantation equipment, e.g., withrespect to cathode re-metallization and replacement.

The disclosure in a further aspect relates to a method of enhancing beamstability and ion source life of a boron doping ion implantation systemincluding a cathode wherein the method includes introducing a borondopant source gas composition to an ion source chamber of the borondoping ion implantation system, operating the boron doping ionimplantation system to ionize the boron dopant source gas composition inthe ion source chamber and generate a beam of boron dopant species thatis directed to a substrate in the ion implantation system for borondoping of the substrate therein with the boron dopant species, whereinthe dopant source gas composition includes (i) boron trifluorideisotopically enriched above natural abundance in boron of atomic mass 11(¹¹B), and (ii) hydrogen, and hydrogen in the dopant source gascomposition is present in an amount of from 2 to 6.99 vol. %, based ontotal volume of boron trifluoride and hydrogen in such composition,wherein a weight change (either growth or loss) of the cathode duringsuch operating is minimized in relation to other hydrogenconcentrations. In such method, the ion source chamber may includecomponents comprising tungsten, e.g., the cathode may comprise atungsten filament. This method will also minimize the change of biaspower and filament current. It will thereby provide benefit for stablebeam conditions and longer source life than would be attainableutilizing isotopically enriched boron trifluoride without the presenceof hydrogen. In some embodiments, hydrogen may be present theabove-described hydrogenated isotopically enriched boron trifluoride(BF₃) dopant source gas composition in an amount ranging from 2 to 6.5vol. %, based on total volume of boron trifluoride and hydrogen in suchcomposition, ranging from 2.5 to 6.25 vol. %, based on total volume ofboron trifluoride and hydrogen in such composition, ranging from 3 to 6vol. %, based on total volume of boron trifluoride and hydrogen in suchcomposition, from about 4 to 6 vol. % or in an amount of 5 vol. %, basedon total volume of boron trifluoride and hydrogen in said composition.

Referring now to the drawings, FIG. 1 is a schematic cross-sectionalview of an exemplary fluid supply package 200 including apressure-regulated fluid storage and dispensing vessel in which thehydrogenated enriched boron trifluoride dopant source gas composition ofthe present disclosure may be provided for storage and dispensing of thecomposition. The gas supply vessels described in U.S. Pat. Nos.6,101,816; 6,089,027; and 6,343,476 issued to Luping Wang, et al. andcommercially available from Entegris, Inc. (Billerica, Mass., USA) underthe trademark VAC are one example, in which one or more gas pressureregulators may be disposed in an interior volume of a gas supply vessel,to provide for dispensing of gas at low pressure, e.g., subatmosphericpressure, for applications such as ion implantation in which lowpressure source gas compositions are used to generate ionic species forion implantation, in apparatus that is operated at corresponding lowpressure.

The fluid supply package 200 includes a fluid storage and dispensingvessel 212 comprising a cylindrical sidewall 214 and a floor 216corporately enclosing the interior volume 218 of the vessel. The sidewall and floor may be formed of any suitable material of construction,e.g., metal, gas-impermeable plastic, fiber-resin composite material,etc., as appropriate to the pressure levels to be maintained in thevessel in storage and dispensing use.

At its upper end 220, the vessel features a neck 221 defining a portopening 222 bounded by the inner wall 223 of the neck 221. The innerwall 223 may be threaded or otherwise complementarily configured tomateably engage therein a valve head 225 including valve body 226 thatmay be complementarily threaded or otherwise configured for suchengagement.

In such manner, the valve head 225 is engaged with the vessel 212 in aleak-tight manner, to hold the hydrogenated isotopically enriched borontrifluoride (BF₃) dopant source gas composition therein in the interiorvolume 218 at the desired storage conditions.

The valve head body 226 is formed with a central vertical passage 228therein for dispensing of the hydrogenated isotopically enriched borontrifluoride (BF₃) dopant source gas composition from the vessel 212. Thecentral vertical passage 228 communicates with the fluid dischargepassage 230 of fluid discharge port 229, as shown.

The valve head body contains a valve element 227 that is coupled withthe valve actuator 238 (hand wheel or pneumatic actuator), for selectivemanual or automated opening or closing of the valve. In this fashion,the valve actuator may be opened to flow gas through the centralvertical passage 228 to the fluid discharge port 229, or alternativelythe valve actuator may be physically closed, to terminate flow of thehydrogenated isotopically enriched boron trifluoride (BF₃) dopant sourcegas composition from the central vertical passage 228 to the fluiddischarge port 229 during the dispensing operation.

The valve actuator thus can be any of various suitable types, e.g.,manual actuators, pneumatic actuators, electromechanical actuators,etc., or any other suitable devices for opening and closing the valve inthe valve head.

The valve element 227 is therefore arranged downstream of the regulator,so that the hydrogenated isotopically enriched boron trifluoride (BF₃)dopant source gas composition dispensed from the vessel flows throughthe regulator prior to flow through the flow control valve comprisingvalve element 227.

The valve head body 226 also contains a fill passage 232 formed thereinto communicate at its upper end with a fill port 234. The fill port 234is shown in the FIG. 1 drawing as capped by fill port cap 236, toprotect the fill port from contamination or damage when the vessel hasbeen filled and placed into use for the storage and dispensing of thehydrogenated isotopically enriched boron trifluoride (BF₃) dopant sourcegas composition.

The fill passage at its lower end exits the valve head body 226 at abottom surface thereof as shown. When the fill port 234 is coupled witha source of the hydrogenated isotopically enriched boron trifluoride(BF₃) dopant source gas composition to be contained in the vessel, thegas can flow through the fill passage and into the interior volume 218of the vessel 212.

Joined to the lower end of valve head body 226 is an extension tube 240,containing an upper particle filter 239 therein. Upper regulator 242 ismounted on the end of the extension tube 240. The upper regulator 242 issecured to the extension tube lower end in any suitable manner, as forexample by providing internal threading in the lower end portion of theextension tube, with which the regulator 242 is threadably enagageable.

Alternatively, the upper regulator may be joined to the lower end of theextension tube by compression fittings or other leak-tight vacuum andpressure fittings, or by being bonded thereto, e.g., by welding,brazing, soldering, melt-bonding, or by suitable mechanical joiningmeans and/or methods, etc.

The upper regulator 242 is arranged in series relationship with a lowerregulator 260, as shown. For such purpose, the upper and lowerregulators may be threadably engageable with one another, bycomplementary threading comprising threading on the lower extensionportion of the upper regulator 242, and threading that is mateablyengageable therewith on the upper extension portion of the lowerregulator 260.

Alternatively, the upper and lower regulators may be joined to oneanother in any suitable manner, as for example by coupling or fittingmeans, by adhesive bonding, welding, brazing, soldering, etc., or theupper and lower regulators may be integrally constructed as componentsof a dual regulator assembly.

At its lower end, the lower regulator 260 is joined to high efficiencyparticle filter 246.

The high efficiency particle filter 246 serves to prevent contaminationof the regulator elements and valve element 227 with particulates orother contaminating species that otherwise may be present in thehydrogenated isotopically enriched boron trifluoride (BF₃) dopant sourcegas composition flowed through the regulators and valves in theoperation of the apparatus.

The embodiment shown in FIG. 1 also has a high efficiency particlefilter 239 disposed in the extension tube 240, to provide furtherparticulate removal capability, and to ensure high purity of thedispensed hydrogenated isotopically enriched boron trifluoride (BF₃)dopant source gas composition.

Preferably, the regulator has at least one particle filter in seriesflow relationship with it. Preferably, as shown in the FIG. 1embodiment, the system includes a particle filter upstream of theregulator(s), as well as a particle filter downstream of theregulator(s), in the fluid flow path from the vessel interior volume 218to the fluid discharge port 229.

The valve head 225 in the FIG. 1 embodiment thus provides a two-portvalve head assembly—one port is the gas fill port 234, and another portis the gas discharge port 229.

The pressure regulators in the FIG. 1 embodiment are each of a typeincluding a diaphragm element coupled with a poppet-retaining wafer. Thewafer in turn is connected to the stem of a poppet element, as part of apressure sensing assembly that precisely controls outlet fluid pressure.A slight increase in outlet pressure above set point causes the pressuresensing assembly to contract, and a slight decrease in the outletpressure causes the pressure sensing assembly to expand. The contractionor expansion serves to translate the poppet element to provide precisepressure control. The pressure sensing assembly has a set point that ispre-established or set for the given application of the fluid storageand dispensing system.

As illustrated, a gas discharge line 266, containing a flow controldevice 268 therein, is coupled with the discharge port 229. By thisarrangement, the flow control device in the gas discharge line is openedto flow gas from the vessel 212 to the associated ion implantationprocess facility 270 (e.g., in a semiconductor manufacturing plant,flat-panel display manufacturing plant, solar panel manufacturing plant,or other process facility in which an ion implantation apparatus isdeployed for boron for doping of substrate particles), in the dispensingmode of the fluid storage and dispensing package 200, when hydrogenatedisotopically enriched boron trifluoride (BF₃) dopant source gascomposition from the storage and dispensing vessel is flowed through theupstream (lower) regulator 260 and then through the downstream (upper)regulator 242 to the valve head to the discharge port 229. The flowcontrol device 268 may be of any suitable type, and in variousembodiments may comprise a mass flow controller.

The hydrogenated isotopically enriched boron trifluoride (BF₃) dopantsource gas composition dispensed in such manner will be at a pressuredetermined by the set point of the regulator 242.

The respective set points of the regulator 260 and the regulator 242 inthe FIG. 1 embodiment may be selected or preset at any suitable valuesto accommodate a specific desired boron ion implantation end useapplication.

For example, the lower (upstream) regulator 260 may have a set pointthat is in a range of from about 20 psig to about 2500 psig. The upper(downstream) regulator 242 may have a set point that is above thepressure set point of the lower (upstream) regulator 260, e.g., in arange of from about 1 torr up to 2500 psig.

In one illustrative embodiment, the lower (upstream) regulator 260 has aset point pressure value that is in the range of from about 100 psig toabout 1500 psig, while the upper (downstream) regulator 242 has a setpoint pressure value in the range of from about 100 torr to about 50psig, wherein the lower (upstream) pressure set point is above the setpoint of the upper (downstream) regulator.

Although the set points of the regulators in a serial regulator assemblymay be established in any suitable ratio in relation to one another, ina two-regulator assembly such as shown in FIG. 1, the upstream regulatorin preferred practice advantageously has a pressure set point that is atleast twice the set point value (measured in the same pressure units ofmeasurement) of the downstream regulator.

In the FIG. 1 embodiment, the lower and upper regulators are coaxiallyaligned with one another to form a regulator assembly having particulatefilters on either end. As a consequence of such arrangement, thehydrogenated isotopically enriched boron trifluoride (BF₃) dopant sourcegas composition dispensed from the vessel 212 is of extremely highpurity.

As a further modification, the particulate filters may be coated orimpregnated with a chemical adsorbent that is selective for impurityspecies present in the hydrogenated isotopically enriched borontrifluoride (BF₃) dopant source gas composition to be dispensed (e.g.,decomposition products deriving from reaction or degradation of the gasin the vessel). In this manner, the hydrogenated isotopically enrichedboron trifluoride (BF₃) dopant source gas composition flowing throughthe particulate filter is purified in situ along the flow path as it isbeing dispensed.

In one illustrative embodiment of a fluid storage and dispensing systemof the type shown in FIG. 1, the vessel 212 is a 3AA 2015 DOT 2.2 litercylinder. The high efficiency particle filter 246 is a GasShield™ PENTA™point-of-use fluid filter, commercially available from Mott Corporation(Farmington, Conn.), having a sintered metal filtration medium in ahousing of 316L VAR/electropolished stainless steel or nickel capable ofgreater than 99.9999999% removal of particles down to 0.003 microndiameter. The high efficiency particle filter 239 is a Mott standard6610-¼ in-line filter, commercially available from Mott Corporation(Farmington, Conn.). The regulators are HF series Swagelok® pressureregulators, with the upper (downstream) regulator 242 having a set pointpressure in the range of from 100 Torr to 100 psig, and the lower(upstream) regulator 260 having a set point pressure in the range offrom 100 psig to 1500 psig, and with the set point pressure of the lower(upstream) regulator 260 being at least twice the set point pressure ofthe upper (downstream) regulator 242. In a specific embodiment, theupper (downstream) regulator 242 may have an inlet pressure of 100 psigand outlet pressure of 500 torr, and the lower (upstream) regulator 260may have an inlet pressure of 1500 psig and outlet pressure of 100 psig.

FIG. 2 is a schematic representation of an ion implantation systemillustrating modes of operation according to the present disclosure inwhich in which a hydrogenated enriched boron trifluoride dopant sourcegas composition of the present disclosure is supplied to an ionimplanter for implantation of boron in a substrate.

As illustrated in FIG. 2, implantation system 10 includes an ionimplanter 12 that is arranged in receiving relationship to gas supplypackages 14, 16 and 18, for delivering gas to the implanter.

Gas supply package 14 includes a vessel containing gas. In some cases,the vessel includes a valve head assembly 22 with a discharge port 24joined to gas feed line 44. The valve head assembly 22 is equipped witha hand wheel 38, for manual adjustment of the valve in the valve headassembly, to translate same between fully open and fully closedpositions, as desired, to effect dispensing or alternatively, closedstorage, of the gas contained in vessel 20. In lieu of the provision ofthe hand wheel 38, the gas supply package 14 may be provided with anautomatic valve actuator, e.g., a solenoid or pneumatic valve actuator,for translating the valve in the valve head assembly of the package toappropriate open or closed position.

Gases can be also contained in the gas supply packages 16 and 18, eachconstructed in similar manner to gas supply package 14. Gas supplypackage 16 comprises a vessel 26 equipped with a valve head assembly 28to which is coupled a hand wheel 40, or alternatively an actuator forthe valve in the valve head assembly. The valve head assembly 28includes a discharge port 30 to which is joined a gas feed line 52.Similarly, gas supply package 18 includes vessel 32 equipped with avalve head assembly 34 to which is coupled hand wheel 42, or acorresponding actuator, for actuation of the valve in the valve headassembly 34. The valve head assembly 34 also includes discharge port 36joined to gas discharge line 60.

In the arrangement shown, at least one of the gas supply packages 14,16, and 18 may contain the hydrogenated isotopically enriched borontrifluoride (BF₃) dopant source gas composition of the presentdisclosure, for sequential supply of such gas composition to the ionimplanter 12. Additionally or alternatively, one of the gas supplypackages, e.g., gas supply package 14, may contain hydrogen, and anotherof the gas supply packages, e.g., gas supply package 16, may containisotopically enriched boron trifluoride, to enable the hydrogenatedisotopically enriched boron trifluoride (BF₃) dopant source gascomposition to be made up at the point of use, by flowing the hydrogenand boron trifluoride components of the composition, in the respectivegas feed lines 44 and 52, to the mixing chamber 68. Gas supply package18 in such arrangement may contain additional isotopically enrichedboron trifluoride, so that both gas supply packages 16 and 18 provideisotopically enriched BF₃, whereby when gas supply package 16 isexhausted of its inventory of boron trifluoride, the valve in the valvehead of gas supply package 16 may be closed, and active dispensing ofthe isotopically enriched boron trifluoride switched to gas supplypackage 18, upon opening of the valve in the valve head of gas supplypackage 18. Such arrangement accommodates the relative proportions inthe hydrogenated isotopically enriched boron trifluoride (BF₃) dopantsource gas composition, in which hydrogen gas is added in a minor amountto the isotopically enriched boron trifluoride.

Accordingly, the present disclosure contemplates a dopant source gascomposition supply kit, comprising (a) a boron dopant gas compositionsupply package, said boron dopant gas composition supply packagecomprising a first gas storage and dispensing vessel containing anisotopically enriched boron trifluoride (BF₃) dopant source gascomposition, and (b) a hydrogen gas supply package, said hydrogen gassupply package comprising a second gas storage and dispensing vesselcontaining hydrogen gas.

As a further variation of the system shown in FIG. 2, each of gas supplypackages 14 and 16 may contain the hydrogenated isotopically enrichedboron trifluoride (BF₃) dopant source gas composition, so that uponexhaustion of an on-stream one of such packages, the other gas supplypackage can be switched into dispensing operation, for continuity ofboron doping operation in the ion implanter, and gas supply package 18may contain a cleaning gas. In such variation arrangement, the borondoping operation can be carried out with dispensing of the hydrogenatedisotopically enriched boron trifluoride (BF₃) dopant source gascomposition from each of the gas supply packages 14 and 16 in sequence,and after the boron doping operation has been concluded, such packagescan be switched out for fresh packages of the hydrogenated isotopicallyenriched boron trifluoride (BF₃) dopant source gas composition, whilethe valve in gas supply package 18 is opened, to dispense cleaning gasto the flow circuitry and downstream ion implanter 12. For such purpose,the gas supply package 18 may contain any suitable cleaning gas, as forexample nitrogen trifluoride, xenon difluoride, hydrogen fluoride, orother appropriate cleaning gas.

For the purpose of controlling flow from the respective gas supplypackages, the respective gas feed lines 44, 52 and 60 are provided withflow control valves 46, 54 and 62 therein, respectively.

Flow control valve 46 is equipped with an automatic valve actuator 48,having signal transmission line 50 connecting the actuator to CPU 78,whereby CPU 78 can transmit control signals in signal transmission line50 to the valve actuator to modulate the position of the valve 46, tocorrespondingly control the flow of gas from vessel 20 to the mixingchamber 68.

In like manner, gas discharge line 52 contains flow control valve 54coupled with valve actuator 56 that in turn is coupled by signaltransmission line 58 to the CPU 78. Correspondingly, flow control valve62 in gas discharge line 60 is equipped with valve actuator 64 coupledby signal transmission line 66 to the CPU 78.

In this manner, the CPU can operatively control the flow of therespective gases from the corresponding vessels 20, 26 and 32.

In the event that gases are concurrently flowed (co-flowed) to mixingchamber 68, as in the case of mixing of hydrogen from one of the vesselswith isotopically enriched boron trifluoride from another or others ofsuch vessels, the resulting gas composition after mixing in mixingchamber 68 is then discharged to feed line 70 for passage to the ionimplanter 12. Accordingly, the disclosure contemplates a method ofoperating an ion implantation system, in which ¹¹B-isotopically enrichedboron trifluoride from a first gas supply package is co-flowed to theion source chamber of the ion implantation system with hydrogen gas froma second gas supply package, at relative rates of the boron trifluorideand hydrogen gases to constitute a dopant source gas composition in theion source chamber comprising (i) boron trifluoride isotopicallyenriched above natural abundance in boron of atomic mass 11 (¹¹B), and(ii) hydrogen in an amount of from 2 to 6.99 vol. %, based on totalvolume of boron trifluoride and hydrogen in such composition.

Correspondingly, if only a single gas supply package 14, 16 or 18 isoperated in dispensing mode, the corresponding hydrogenated isotopicallyenriched boron trifluoride (BF₃) dopant source gas composition thenflows through the mixing chamber, as modulated by the associated flowcontrol valve, and is passed in feed line 70 to the ion implanter.

Feed line 70 is coupled with a bypass flow loop comprised of bypasslines 72 and 76 communicating with the feed line, and with gas analyzer74. The gas analyzer 74 thus receives a side stream from the main flowin feed line 70, and responsively generates a monitoring signalcorrelative of the concentration, flow rate, etc. of the gas stream andtransmits a monitoring signal in the signal transmission line couplingthe analyzer 74 with CPU 78. In such manner, the CPU 78 receives themonitoring signal from gas analyzer 74, processes same and responsivelygenerates output control signals that are sent to the respective valveactuators 48, 56 and 64, or selected one or ones thereof, asappropriate, to effect the desired dispensing operation of thehydrogenated isotopically enriched boron trifluoride (BF₃) dopant sourcegas composition to the ion implanter. The gas analyzer 74 and the CPU78, with their ancillary signal transmission lines and actuators,constitute a monitoring and control system that may be operativelyemployed to the land hydrogen and isotopically enriched borontrifluoride to form the hydrogenated isotopically enriched borontrifluoride (BF₃) dopant source gas composition containing hydrogen atthe desired concentration.

The ion implanter 12 produces an effluent that is flowed in effluentline 80 to effluent treatment unit 82, which may treat the effluent byeffluent treatment operations including scrubbing, catalytic oxidation,etc., to generate a treated gas effluent that is discharged from thetreatment unit 82 in vent line 84, and may be passed to furthertreatment or other disposition.

The CPU 78 may be of any suitable type, and may variously comprise ageneral purpose programmable computer, a special purpose programmablecomputer, a programmable logic controller, microprocessor, or othercomputational unit that is effective for signal processing of themonitoring signal and generation of an output control signal or signals,as above described.

The CPU thus may be programmatically configured to effect a cyclicoperation including concurrent flow of gases from two or all three ofthe sources 14, 16 and 18, or alternatively with the respective gasesbeing flowed in sequence. Thus, any flow mode involving co-flow ormixtures of gases, or sequential gas flows, may be accommodated.

It will therefore be recognized that boron doping of a substrate in theion implanter may be carried out in any of various manners, to utilizethe hydrogenated isotopically enriched boron trifluoride (BF₃) dopantsource gas composition as a premixed gas composition, or with point ofuse mixing of hydrogen and enriched boron trifluoride from separate gassupply packages, or in combination or sequence with other gas species.It will therefore be appreciated that the hydrogenated isotopicallyenriched boron trifluoride (BF₃) dopant source gas composition may bevariously used along with hydride gas, fluoride gas, noble gas, oxidegas or other gas in various implementations of the ion implantationsystem shown in FIG. 1, or in ion implantation systems correspondinglyconfigured for operation in accordance with the disclosure.

It will therefore be appreciated that the hydrogenated isotopicallyenriched boron trifluoride (BF₃) dopant source gas composition of thepresent disclosure may be provided as a premixed composition, oralternatively as made up at the point of use from respective gas supplypackages of the hydrogen and boron trifluoride components of suchcomposition, as may be desired in a given implementation of the dopantsource gas composition of the present disclosure, in specific ionimplantation facilities.

Referring now to FIG. 3, a graph is shown of B+ beam current, inmilliamps, as a function of hydrogen/enriched boron trifluoride co-flowratio (volume H₂/volume BF₃ from 0 to 0.6) flowed to an ion chamber ofan ion implantation apparatus, with an isotopically enriched BF₃ flowrate of 2.75 standard cubic centimeters per minute (sccm), showing thebeam performance of hydrogenated isotopically enriched boron trifluoridedopant source gas compositions of the present disclosure.

The enriched boron trifluoride gas in the hydrogenated isotopicallyenriched boron trifluoride dopant source gas composition used togenerate the data shown in FIG. 3 was substantially pure (>99.95 vol. %)¹¹BF₃. The arc voltage of the ion implantation apparatus employed togenerate such data was 90 V, with a source beam current of 25 mA, and anextraction voltage of 20 kV.

The data in FIG. 3 show that the B+ beam current for isotopicallyenriched BF₃ alone is approximately 6.5 mA. It has been found that athydrogen/boron trifluoride co-flow ratio values at 0.07 and above, thebeam current rapidly declines. It has been found that hydrogen/borontrifluoride co-flow ratio values below 0.02 provide inadequate hydrogenfor the suppression of tungsten fluorine reaction and tungstendeposition, coating and cathode growth of tungsten in operation of theion implantation system.

Accordingly, the present disclosure contemplates hydrogen/enriched borontrifluoride dopant source gas compositions for ion implantation ofboron, in which the composition contains from about 2 to about 6.99volume percent of hydrogen, and more particularly about 5% volumepercent of hydrogen, as a compositional range in which beam currentreduction is maintained at a very low level, e.g., in a range of from 0%to 8% reduction of the B+ beam current when compared to a baseline boronion beam current, while the production of F+, W+, and WF_(x)+ beamcomponents is effectively reduced. Accordingly, the hydrogenatedisotopically enriched boron trifluoride compositions of the presentdisclosure enable high boron ion beam currents to be maintained, whilesubstantially reducing the amount of undesired beam components includingtungsten and tungsten fluoride ionic species, to enable source life ofthe cathode to be extended, thereby enhancing the high-efficiencyobtained by use of isotopically enriched boron trifluoride, and reducingthe maintenance required by the ion implantation equipment, e.g., withrespect to cathode re-metallization and replacement.

FIG. 4 is a beam spectrum comparison graph, of beam current, inmilliamps, as a function of atomic mass unit (AMU) value, showing beamcurrent values for B+, F+, HF+, BF+, BF2+, and W++ ions, with an insetspectrum segment showing the beam current values for W+ and WF_(x)+(x=1, 2, 3, 4, 5, and 6) ions in the range of 170-300 AMU, as shown for(i) flow of only substantially pure (>99.95 vol. %) ¹¹BF₃, (ii) co-flowof hydrogen with the substantially pure (>99.95 vol. %) ¹¹BF₃, at a lowH₂/¹¹BF₃ volumetric ratio, and (iii) co-flow of hydrogen with thesubstantially pure (>99.95 vol. %) ¹¹BF₃, at a high H₂/¹¹BF₃ volumetricratio. The flow rate of the substantially pure ¹¹BF₃ was 2.75 sccm, andthe source beam current was 25 mA, with the arc voltage being 90 V, andthe extraction voltage being 20 kV, in all test runs.

The data in FIG. 4 show that hydrogen co-flow is effective tosignificantly reduce the generation of W+ and WF_(x) (x=1, 2, 3, 4, 5,and 6) beam spectrum components, below the levels that are generated inthe absence of hydrogen.

FIG. 5 is a graph of F+, HF+, W+, and WF+ beam currents, in milliamps,as a function of H₂/¹¹BF₃ volumetric ratio from 0 to 0.6, wherein datafor the respective ion species are represented by diamond symbols (♦)for F+, circular dot symbols (▪) for HF+, square symbols (▪) for W+, andtriangular symbols (▴) for WF+. The boron trifluoride employed togenerate such data was substantially pure (>99.95 vol. %) ¹¹BF₃. Theboron trifluoride employed to generate such data was substantially pure(>99.95 vol. %) ¹¹BF₃.

The data in FIG. 5 show that F+, W+, and WF+ beam currents aresubstantially reduced by presence of hydrogen. It has been found thatHF+ beam current can be maintained at a very low level in the 2 to 6.99vol. % H₂, and more particularly about 5 vol. % H2 concentration rangeof the H₂/enBF₃ dopant source gas compositions of the presentdisclosure.

FIG. 6 is a graph of the corresponding normalized F+, HF+, W+, and WF+beam currents, in milliamps, as a function of H₂/¹¹BF₃ volumetric ratiofrom 0 to 0.6, wherein F+, HF+, W+, and WF+ beam currents have beennormalized to B+ beam currents, with data for the respective ion speciesare represented by diamond symbols (♦) for F+, circular dot symbols (●)for HF+, square symbols (▪) for W+, and triangular symbols (▴) for WF+.

The dopant source gas compositions of the present disclosure thereforeprovide an effective balance in maintaining high beam current of theboron implant species, while at the same time reducing W+ and WF_(x)+(x=1, 2, 3, 4, 5, and 6) beam currents and tungsten fluoride reaction.The reduction in the beam current of a selected boron implant speciessuch as, for example, B+ or BF2+, can be determined by comparing theboron implant species beam current when hydrogen is present in thedopant gas in selected amounts to the boron implant species beam currentin the absence of hydrogen. In some cases, a reduction in the boronimplant species beam current can range from 0% to less than 10%; from 0%to less than 9%; from 0% to less than 8%; or from 0% to less than about5%. This balance may help to reduce tungsten deposition, coating andcathode growth of tungsten. An appropriate balance of borontrifluoride/hydrogen mixture may also be used to prevent so-called“punch through” of the cathode due to sputtering.

The dopant source gas compositions of the present disclosure may beutilized in boron doping applications in which the ion implant system is“tuned” for selection of various boron ionic implant species. Forexample, in various applications, the ion implant system may be tunedfor B+ doping of a substrate. In other applications, the ion implantsystem may be tuned for doping of BF₂+ implant species in the substrate.The dopant source gas compositions of the present disclosure may beadvantageously utilized in any of such ion implant systems tuned for anyof a wide variety of boron ionic implant species.

It is a further surprising aspect of the present disclosure that whenthe ion implantation system is tuned for doping of BF₂+ implant speciesin the substrate, an even higher reduction of the tungsten mass spectralpeak is achieved, in relation to the reduction observed for B+ doping ofa substrate, when using the hydrogenated enriched boron trifluoride gascompositions and more particularly, the hydrogen/enriched borontrifluoride dopant source gas compositions for ion implantation ofboron, in which the composition contains from about 2 to about 6.99volume percent of hydrogen, and more particularly about 5% volumepercent of hydrogen as a compositional range.

A series of tests was conducted, utilizing a commercial indirectlyheated cathode ion source operated at arc power of 120 V and 3.4 A, withextraction voltage of 20 kV, and flow rate of 4 sccm of substantiallypure (>99.95 vol. %) ¹¹BF₃, with the runs involving the hydrogenatedenriched boron trifluoride utilizing the same base flow rate of borontrifluoride (4 sccm) with addition of hydrogen at optimized percentage.In the beam process, the ion source was pre-warmed with argon forapproximately 20 minutes, and the specific implant species beam, eitherB+ or BF₂+, was tuned by optimizing the source magnet, elected position,and analyzer magnet of the ion implantation apparatus. The resultingtest beam was run for 11 hours under optimized conditions to ensure beamstability, and a mass spectrum was generated, followed by post-warmingof the source with argon for approximately 15 minutes.

FIG. 7 is a beam spectrum comparison graph, of beam current, inmilliamps, as a function of atomic mass unit (AMU) value, showing beamcurrent values for B+, F+, BF+, and BF2+ ions, with an inset spectrumsegment showing the beam current values for W+ and WF_(x)+ (x=1, 2, 3,4, 5, and 6) ions in the range of 170-300 AMU, in which the ionimplantation system was tuned for B+ ion implant species in a first run,and for BF₂+ ion implant species in a second run, utilizingnon-hydrogenated substantially pure (>99.95 vol. %) ¹¹BF₃ in both cases.As reflected in the graph, there was significant variation in thefluorine (F+) peak, and in the tungsten (W+) peak in the respectivetuned equipment systems.

FIG. 8 is a beam spectrum comparison graph, of beam current, inmilliamps, as a function of atomic mass unit (AMU) value, showing beamcurrent values for B+, F+, BF+, and BF2+ ions, with an inset spectrumsegment showing the beam current values for W+ and WF_(x)+ (x=1, 2, 3,4, 5, and 6) ions in the range of 170-300 AMU, in which the ionimplantation system was tuned for B+ ion implant species, utilizingnon-hydrogenated substantially pure (>99.95 vol. %) ¹¹BF₃ (greenspectrum) in a first run, and hydrogenated substantially pure (>99.95vol. %) ¹¹BF₃ (red spectrum; H₂/¹¹BF₃ volumetric at optimized ratio) ina second run. As reflected in the graph, a similar B+ beam was generatedin both runs, and the W+ and WF_(x)+ (x=1, 2, 3, 4, 5, and 6) peaks werereduced in the use of the hydrogenated ¹¹BF₃ dopant gas sourcecomposition, as compared to the use of the non-hydrogenated ¹¹BF₃ dopantgas source composition.

FIG. 9 is a beam spectrum comparison graph, of beam current, inmilliamps, as a function of atomic mass unit (AMU) value, showing beamcurrent values for B+, F+, BF+, and BF2+ ions, with an inset spectrumsegment showing the beam current values for W+ and WF₆+ ions in therange of 170-300 AMU, in which the ion implantation system was tuned forBF₂+ ion implant species, utilizing non-hydrogenated substantially pure(>99.95 vol. %) ¹¹BF₃ (green spectrum) in a first run, and hydrogenatedsubstantially pure (>99.95 vol. %) ¹¹BF₃ (red spectrum; H₂/¹¹BF₃volumetric ratio of 0.05) in a second run. As reflected in the graph, asimilar B+ beam was generated in both runs, and the W+ and WF₆+ peakswere significantly reduced in the use of the hydrogenated ¹¹BF₃ dopantgas source composition, as compared to the use of the non-hydrogenated¹¹BF₃ dopant gas source composition.

The data for the respective runs of FIGS. 10, 11, 12 and 13 are set outin Table 1 below.

TABLE 1 Cathode Anti-Cathode Weight Weight Change/ Change/ Source ChangeHour Change Hour Dopant Gas Mixture H2 % (gram) (g/hour) (gram) (g/hour)B+ BF3 Only 0% −1.792 −0.163 −0.886 −0.081 BF3 + H2 (5%) 5% −1.504−0.137 −0.901 −0.082 BF3 + H2 (13%) 13% −1.668 −0.152 −1.250 −0.114 BF2+BF3 Only 0% 0.104 0.009 −0.411 −0.037 BF3 + H2 (5%) 5% −0.277 −0.025−0.417 −0.038 BF3 + H2 (13%) 13% −0.341 −0.031 −0.441 −0.040

FIG. 10 is a graph showing the cathode weight change plotted against thevolume percentage of hydrogen gas where the dopant gas is B+. Asevidenced by FIG. 10, the cathode weight change for BF₃/H₂ at 5% H₂ didnot follow the cathode weight change trend from 0% to 13%. The weightloss of the BF₃/5% H₂ composition was less than either 0% or 13% of H₂.

FIG. 11 is a graph showing the cathode weight change plotted against thevolume percentage of hydrogen gas wherein the dopant gas is B+. As shownin FIG. 11, the anti-cathode weight change for BF₃/H₂ at 5% H₂ also didnot follow trend from 0% to 13%. The weight loss for BF₃/5% H2 wasalmost the same as 0%.

FIG. 12 is a graph showing the cathode weight change plotted against thevolume percentage of hydrogen gas where the dopant gas is BF₂+. Asevidenced by FIG. 10, the cathode weight change for BF₃/H₂ at 5% H₂ didnot follow the cathode weight change trend from 0% to 13%.

FIG. 13 is a graph showing the cathode weight change plotted against thevolume percentage of hydrogen gas wherein the dopant gas is BF₂+. Asshown in FIG. 13, the anti-cathode weight change for BF₃/5% H₂ was moreclose to the 0% H₂ condition and slightly off the 0% to 13% trend.

From the foregoing data, it is seen that bias power was significantlyimpacted by hydrogen in the dopant source gas composition, with B+dopant tuning having a larger bias power change, in relation to BF₂+dopant tuning. Concerning the weight changes of the cathode andanti-cathode components, the use of a hydrogenated ¹¹BF₃ dopant sourcecomposition in accordance with the present invention, in the ionimplantation system tuned for B+ doping, produced a 7% change in cathodeweight loss, as compared to the use of the non-hydrogenated ¹¹BF₃ dopantsource composition. In the ion implantation system tuned for BF₂+doping, the use of a hydrogenated ¹¹BF₃ dopant source composition inaccordance with the present invention yielded a more than four-foldchange in cathode weight loss.

It is a surprising and beneficial result that use of the hydrogenatedisotopically enriched boron trifluoride dopant source gas compositionsof the present disclosure result in less cathode weight loss thancorresponding non-hydrogenated isotopically enriched boron trifluoridedopant source gas compositions, and at the same time produces lesstungsten transport in the ion source. Accordingly, the dopant source gascompositions of the present disclosure achieve a substantial advance inthe art.

While the disclosure has been set forth herein in reference to specificaspects, features and illustrative embodiments, it will be appreciatedthat the utility of the disclosure is not thus limited, but ratherextends to and encompasses numerous other variations, modifications andalternative embodiments, as will suggest themselves to those of ordinaryskill in the field of the present disclosure, based on the descriptionherein. Correspondingly, the disclosure as hereinafter claimed isintended to be broadly construed and interpreted, as including all suchvariations, modifications and alternative embodiments, within its spiritand scope.

What is claimed is:
 1. A hydrogenated isotopically enriched borontrifluoride (BF₃) dopant source gas composition, said compositionconsisting of (i) boron trifluoride isotopically enriched above naturalabundance in boron of atomic mass 11 (¹¹B), and (ii) hydrogen in anamount of from 4 to 6.5 vol. %, based on total volume of borontrifluoride and hydrogen in the composition.
 2. The composition of claim1, wherein the boron trifluoride isotopically enriched above naturalabundance in boron of atomic mass 11 (¹¹B) is isotopically enrichedabove an enrichment level selected from the group consisting of 80.1%,85%, 88%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, 99.995%,and 99.999%.
 3. The composition of claim 1, wherein the borontrifluoride isotopically enriched above natural abundance in boron ofatomic mass 11 (¹¹B) is isotopically enriched above 99%.
 4. Thecomposition of claim 1, wherein hydrogen is present in an amount of from4 to 6 vol. %, based on total volume of boron trifluoride and hydrogenin said composition.
 5. The composition of claim 1, wherein hydrogen ispresent in an amount of 5 vol. %, based on total volume of borontrifluoride and hydrogen in said composition.
 6. A hydrogenatedisotopically enriched boron trifluoride (BF₃) dopant source gascomposition, said composition consisting of (i) boron trifluorideisotopically enriched above 99% in boron of atomic mass 11 (¹¹B), and(ii) hydrogen in an amount of 5 vol. %, based on total volume of borontrifluoride and hydrogen in said composition.
 7. A boron dopant gascomposition supply package, said package comprising a gas storage anddispensing vessel holding a hydrogenated isotopically enriched borontrifluoride (BF₃) dopant source gas composition according to claim
 1. 8.A method of boron on implantation, comprising introducing to an ionsource chamber of an ion implantation system a hydrogenated isotopicallyenriched boron trifluoride (BF₃) dopant source gas composition accordingto claim 1, and ionizing said hydrogenated isotopically enriched borontrifluoride (BF₃) dopant source gas composition in the ion sourcechamber to generate boron-containing implant species for the boron ionimplantation, wherein a beam current of the boron containing implantspecies is reduced less than 8% when hydrogen is present compared to abeam current of the boron containing implant species when no hydrogen ispresent in the ion source chamber.
 9. The method of claim 8, furthercomprising generating a beam of said boron-containing implant species,and directing said beam to a substrate for implantation of theboron-containing implant species therein.
 10. The method of claim 8,comprising exposing a substrate to the boron-containing implant species,for implantation thereof in the substrate.
 11. A method of operating anion implantation system, comprising co-flowing (a) ¹¹B-isotopicallyenriched boron trifluoride from a first gas supply package, and (b)hydrogen gas from a second gas supply package, to an ion source chamberof the ion implantation system, at relative rates of the borontrifluoride and hydrogen gases to constitute a dopant source gascomposition in the ion source chamber consisting of (i) borontrifluoride isotopically enriched above natural abundance in boron ofatomic mass 11 (¹¹B), and (ii) hydrogen in an amount of from 4 to 6.5vol. %, based on total volume of boron trifluoride and hydrogen in suchcomposition.
 12. A method comprising introducing a boron dopant sourcegas composition to an ion source chamber of the boron doping ionimplantation system, operating the boron doping ion implantation systemto ionize the boron dopant source gas composition in the ion sourcechamber and generate a beam of boron dopant species that is directed toa substrate in the ion implantation system for boron doping of thesubstrate therein with the boron dopant species, wherein the dopantsource gas composition consists of (i) boron trifluoride isotopicallyenriched above natural abundance in boron of atomic mass 11 (¹¹B), and(ii) hydrogen in an amount of from 4 to 6.5 vol. %, based on the totalvolume of boron trifluoride and hydrogen in the composition, wherein aweight change of the cathode during said operating, in relation to otherhydrogen concentrations is minimized and beam stability and ion sourcelife is enhanced.
 13. The method of claim 12, wherein the cathodecomprises a tungsten filament.
 14. The method of claim 12, wherein saidhydrogen concentration in the dopant source gas composition concurrentlyminimizes change of bias power and filament current during saidoperating.
 15. The method of claim 12, wherein the boron trifluoride isisotopically enriched above natural abundance in boron of atomic mass 11(¹¹B) is isotopically enriched above 99%.
 16. The method of claim 12,wherein hydrogen is present in an amount of 5 vol. %, based on totalvolume of boron trifluoride and hydrogen in said composition.
 17. Themethod of claim 12, wherein a beam current of a boron ion implantspecies is reduced less than 8% when compared to a beam current of theboron ion implant species when no hydrogen is present in the ion sourcechamber.